Watlow Optimizing Your Process System with the Series 988 Controller - Manual (Page 32)

Optimizing Your Process System with the WATLOW Series 988
General Software Features
3.12
Overview:
The retransmit output can be used to transmit
an analog signal representing the value of
either input process variable or the target set
point variable. The retransmit signal is factory
configured as either a milliamp or a voltage
signal. In choosing the type of retransmit signal
the operator must take into account the input
impedance of the device to be retransmitted to
and the required signal type, either voltage or
milliamps.
Typically applications might use the retransmit
option to record one of the variables with a
Retransmit
chart recorder or to generate a set point for
other controls in a multi-zone application (see
page 3.11).
Requirements:
Output 3 is used for the retransmit option.
Choose output type M (0-20, 4-20mA) or N (0-
5, 1-5 or 0-10VDC), depending on the signal
type. Select the output range in the Output
menu.
Enhanced software is not required for this
feature.
Sample Applications:
The 988 is being used to control the temperature of a heat-treat oven. The
temperature of the process must be recorded on a chart recorder. The
oven temperature range stays between 600 to 900 degrees F. The chart
recorder requires a 4-20mA signal.
In the Output menu set analog output to to tag the input
1 process value as the parameter to be retransmitted. Set retransmit low
limit
to 600 to set the low range for the retransmit signal to 600. Set
retransmit high limit to 900 to set the high range for the retransmit
signal to 900. Set retransmit calibrate offset to 0, assuming there is
no calibration offset required.
The retransmit output will be 4mA until the oven temperature is greater
than 600 degrees F, at which point the signal will increase with tempera-
ture to 20mA at 900 degrees F and will not exceed 20mA.
TL W WA
PROCESS
L1 L2 L3 L4
DEV
% OUT
DISPLAY
MODE
AUTO
MAN
SERIES 988
output 1
Heat-treat Oven
heaters
input 1
limit
sensor
limit
Chart
Recorder
output 3
temperature
sensor